1. Field of the Invention
The present invention relates to position detection devices, and in particular, to position detection devices applicable to robots and other equipment used in automated assembly line manufacturing processes.
2. Prior Art
Various devices are conventionally known, by means of which the position of articles under manufacture on an automated assembly line can be determined, thereby permitting automated equipment for manipulating objects, assembling components, machining, etc. to appropriately orient with respect to the articles under manufacture and components thereof. Typically, these devices employ three pairs of television cameras, each television camera having associated image processing equipment used in conjunction with that camera alone, whereby three-dimensional images of each of three non-collinear reference points on the object, for example, holes or protuberances, are captured and processed. In this way, the article under manufacture is oriented with respect to a virtual Cartesian coordinate system internal to the position detection device, thereby establishing the position and location of the object in relation to the work space and manufacturing devices therein.
These conventional devices have several shortcomings, however, including the following:
1. Six television cameras and individual image processing equipment for each television camera are required, for which reason these devices tend to be highly complex and quite costly. PA1 2. In order to accurately correlate the location of each of the reference points in the work space with coordinates determined therefor based on the composite image of the reference point obtained with a respective pair of television cameras and image processing devices, extensive and time consuming calibration is required. PA1 3. Grey scale processing of each captured image is generally required in order to enhance contrast. For this reason, significant time delays in establishing the position of an object under manufacture must be tolerated unless highly expensive computational equipment having massive processing power is utilized. Accordingly, real-time manufacturing control is quite difficult to achieve with these conventional position detection devices. PA1 a) first position detection means for optically, or by means of direct contact with the workpiece, mechanically detecting the point of intersection of a line containing a first straight edge among the straight edges of the workpiece and a first detection plane defined within the work space; PA1 b) second position detection means for optically, or by means of direct contact with the workpiece, mechanically detecting the point of intersection of a line containing a second straight edge among the straight edges of the workpiece which is different from the above mentioned first straight edge and a second and third detection plane defined within the work space; PA1 c) storage means for storing data representing the geometric relationship between the above mentioned first straight edge and second straight edge of the workpiece; and PA1 d) computational means for calculating the position and orientation of the workpiece based on the data stored in the above mentioned storage means and on the coordinates of the points of intersection detected by the above mentioned first position detection means and second position detection means. PA1 1. For any workpiece having two or more non-collinear straight edges, position detection can be carried out using any two of the non-collinear straight edges. For this reason, there are no particular limitations concerning the position of the device. PA1 2. For workpieces having substantially lengthy straight edges, measurement can be carried out even when the workpiece is considerably shifted from a standard position. Thus, position detection can be accomplished over a wide range of positions with respect to the workpiece. PA1 3. Necessary calculations are limited in number as well as in complexity, for which reason the position of a workpiece can be assessed in a very short period of time. For the same reason, processing power requirements for computational circuits incorporated in the device are minimal. Thus, the device of the present invention is applicable to manufacturing facilities employing real-time manufacturing control systems. PA1 4. During calibration, adjustments connected with each detection plane need be carried out with respect to only two dimensions, thus considerably simplifying and accelerating calibration. PA1 5. Contrast intensity adjustments can be carried out based on measurements taken using a standard contrast pattern. Furthermore, during processing of video or tactile data, each point on each of the detection planes can be adequately represented by a single bit binary format, that is, each bit is either on or off. Thus, since grey scale processing and the like is eliminated, data processing is markedly accelerated compared with conventional methods and processing power requirements are therefore minimal. For these reasons and considerations mentioned in #3 above, the present invention is very much applicable to manufacturing facilities employing real-time manufacturing control systems. PA1 6. Only data describing the spatial relationship between the first and second straight edge of each workpiece for which measurements will be carried out are required. Accordingly, data storage requirements are minimal. PA1 7. Since it is possible to carry out measurements with the apparatus of the present invention using tactile detection means, further enhancement of the accuracy of position detection is possible.